Strand tensioning apparatus



April 1, 1950 E. D. HANSON 0 2,504,020

STRAND TENSIONING APPARATUS Filed Oct. 1a, 1946 mvs/v TOR E. D. HANSON A rr omvsr Patented Apr. 11, 1950 vn l-i020 2,504,020 STRAND TENSIONING APPARATUS Estyle D. Hanson, Baltimore, Md., assignor to Western Electric Company, Incorporated, New York, N. Y., a corporation of New York Application October 18, 1946, Serial No. 704,131

Claims.

This invention relates to strand tensioning ap- Daratus, and more particularly to tension brakes for maintaining uniform tension on strands being drawn from supply cops. l

Certain types of serving heads revolve a plurality of cops having textile strands wound thereon about a conductor being continuously advanced along the turning axis of the serving head and thereby serve a textile covering over the advancing conductor. The serving operation withdraws the textile strand from the cops, causing them to be rotated at relatively high speeds. The cops cannot be permitted to rotate freely on their supporting spindle because it is necessary to maintain a uniform tension on each of the strands in order for the textile cover to be properly formed on the conductor.

To maintain uniform tension on the individual strands, it has been suggested that a spring pressed paddle be directed against the periphery of the cop to exert a braking effect on the strand being withdrawn therefrom. It is well known that this type of brake will not maintain uniform tension on the thread throughout the unwinding operation from a full cop to an empty cop due to the fact that as the unwinding progresses, the diameter of the cop decreases and the pressure exerted by the paddle against the periphery of the cop decreases due to the relaxation of the spring which urges the paddle toward the cop. Since the rate of decrease in pressure exerted by the paddle against the cop periphery in this type of brake is not directly proportional to the rate of reduction taking place in the cop diameter, the tension on the strand varies during the serving operation. Further, when ordinary paddle brakes are employed in high speed serving heads, their braking ability is critically affected by the action of centrifugal force thereon.

The present invention overcomes these diificulties by providing a counterweighted, spring pressed paddle brake arm arranged with respect to a strand supply cop rotatably mounted on the serving head rotor so that its neutral position with respect to the axis of rotation of the serving head rotor falls at a position intermediate its innermost and outermost braking positions. The counterweight serves to overcome the effect of centrifugal force on the brake arm when the serving head is rotating and permits the brake spring to maintain the proper tension on the strand being withdrawn from the cop as the brake arm moves from its outermost braking po sition to its innermost braking position,

An object of the invention is to provide new and improved strand tensioning apparatus.

Another object of the invention is to provide a tension brake which will maintain uniform tension on the thread being withdrawn from a cop carried by a serving head rotor.

A complete understanding of the invention may be obtained from the following detailed description of a specific embodiment thereof, when read in conjunction with the appended drawing, in which:

Fig. 1 is a vertical; sectional view of a typical serving head on which is mountedthe strand tensioning apparatus constituting a specific embodiment of the invention.

Fig. 2 is an enlarged view of a portion of the apparatus shown in Fig. 1;

Fig. 3 is an enlarged, vertical, sectional view taken along line 33 of Fig. 2, and

Fig. 4 is a vertical, sectional view taken along line 4-4 of Fig. 3.

Referring now to the drawing and more particularly to Fig. 1, there is illustrated only so much of a serving head I0 as is necessary to a proper understanding of the invention and the operation thereof. prises a base plate H which serves to support a large central hub 12 on which is rotatably mount ed a serving head rotor 13 having a drive pulley l4 rigidly secured thereto. The rotor I3 is revolved about the central axis of the serving head H) at relatively high speed by suitable driving means (not shown) connected to the pulley H by means of a V-belt I5. A plurality of cops l6i6 having a textile strand wound thereon are positioned on spindles l9-|9 provided on the rotor I3 adjacent to its outer periphery. When the rotor 13 is being rotated, the textile strands are withdrawn from the cops IB|6 to serve a textile covering ll over a core unit I8 being advanced through the central axis of the serving head It) in a manner to be hereinafter described.

For the purpose of illustrating the present invention it will be assumed that the serving head I 0 is rigidly secured on the end of a fiyer-type twisting machine (not shown) substantially the same as that disclosed in G. E. Henning et a1. Patent 2,338,848, issued September 7, 1943. The twisting machine serves to advance a plurality of filamentary strands 20-20 from a suitable supply (not shown) over a plurality of guide rollers 2l--2| disposed on a gathering plate 22 adjustably positioned to the left of the serving head I! and to twist the strands 20-40 about a stay cord 23 advanced axially of the apparatus to form The serving head In comthe core unit II. The serving head II is secured to the twisting machine for the purpose of serving the textile covering i'l over the core ll being advanced by said twisting machine along the central axis of the serving head.

To perform the serving operation on the core II, the serving head rotor |3 must be rotated at a rate of speed substantially greater than that at which the core I4 is being rotated, which causes strands 24-24 to be withdrawn from their respective cops |--li at a relatively high rate of speed. The strands are advanced through a plurality of guides 2525 and a plurality of guide slots 26-46 provided in the hub of the rotor l3 and are served spirally around the rotating and advancing core unit I 3 to form a textile covering I l thereover. In order for the textile covering to be properly formed over the core unit it, a predetermined uniform tension must be maintained on the strands 24-24 throughout the entire time the strands are being withdrawn from the cops iB-IO.

To maintain a uniform tension on the strands 2424, a plurality of paddle-type brakes 33-30 are mounted on the rotor 3, with each brake adjacent to one of the cops |6|5. Each of the paddle type brakes 3ll3|i comprises a curved arm 3| (Fig. 2) having one end secured to the free end of a shaft 32 rotatably supported in a tubular bearing 33 rigidly secured on the rotor l3. A portion of the opposite end of the shaft 32 is arranged to extend beyond the right face of the rotor l3 and is provided with a slot 34 for receiving the end of the inside coil of a torsion spring 35, having the end of its outside coil secured to a housing 38 by means of a rivet 31. The housing 36 is provided with an annular flange 33 having a pair of diametrically opposed locking holes 4040 which engage a pair of spaced locking pins 4|-4| (Fig. 3) secured in the rotor l3. A nut 43 is threadedly positioned on the end of the shaft 32 to slidably maintain the underneath edge of the arm 3| against the upper end of the bearing 33 and to centrally position the slot 34 of the shaft 32 within the spring housing 35. A counterweight 44 (Figs. 2 and 3) is positioned on the free end of the shaft 32 directly opposite the fixed end of the arm 3|, which counterweight is designed to have a mass substantially equal to the brake arm 3|. The brake arm 3| and the counterweight 44 are thereby arranged on the shaft 32 so that they rotate in the bearing 33 as a unit.

The brake 30 is positioned on the rotor i3 with respect to the cop It so that the torsion spring 35 will continuously urge the free end of the arni 3| against the periphery of the cop IS. The upper end of the bearing 33 has an arcuate portion removed therefrom to form an opening 45 (Fig. 4), the end walls of which serve to limit the movement of a pin 45 secured in the shaft 32. The opening 45 controls the total movement of the arm 3|, and is designed to permit the arm 3| to move through a slightly larger arc than that required by the arm to continuously engage the periphery of the cop from a full cop to an empty cop. The pin 45 abuts the right hand wall of the opening 45 (Fig. 4) and serves to prevent rotation of the shaft 32 when the torsion,

spring 35 is being loaded to the required amount. The torsion spring is loaded by turning the housing 35 in a counterclockwise direction when viewed in Fig. 2, a given number of turns and" then the housing is manipulated until the locking holes 44-40 engage the pins 4|-4|. In order to assemble a cop, such as a cop It on the rotor l3, it is merely necessary to move the arm 3| to the left, as seen in Fig. 2, against the action of the spring 35 until the pin abuts the left wall of the opening 45 (Fig. 4), then to slide the cop on the spindle l3 and finally to release the arm 3|, whereupon the spring 35 moves the end of the arm to the right until it abuts the periphery of the cop I6.

Referring to Fig. 2, the shaft 32 is secured on the rotor l3 so that the center of rotation of the rotor and the pivot point of the brake arm 3| are radially aligned with each other, in which case, the line x:r can be considered as passing through the pivot point of the arm and center of rotation of the rotor. The arm 3| is so curved and has the counterweight 44 so arranged on the end of the shaft 32 with respect to the arm 3| that the arm and I counterweight assembly, when free of the action of the torsion spring 35, assumes a neutral position with respect to the line :r$, which position is indicated by the letter A in Fig. 2. When the arm 3| is in the neutral position (A), there is no tendency for the assembly to rotate about its pivot point in either direction when the serving head rotor I3 is rotated at high speed. The brake 30 is positioned on the rotor i3 so that when a full cop i6 is positioned on the spindle IS, the arm 3| assumes its outermost braking position with respect to the cop as indicated by the letter B, which position is substantially to the left of the neutral position (A) of the arm. As the strand 24 is withdrawn from the cop i8 by a serving operation on the core l8, the torsion spring causes the arm 3| to eventually assume its innermost braking position with respect to the cop as indicated by the letter C, which position is substantially to the right of the neutral position (A) of the arm.

When the arm 3| is in the B position the free end thereof engages the periphery of the cop It at a point substantially adjacent to the end of the arm. The arm 3| is curved concavely with respect to the periphery of the cop l6, so that when the arm 3| assumes the C position, its contact point with the periphery of the cop has moved closer to the pivot point of the arm. In other words, as the diameter of the cop i6 decreases, the efiective braking length of the arm 3| is decreased. It should be noted, since the arm 3| and counterweight 44 are arranged as a pivotally mounted unit in the bearing 33, that when the unit moves from its B position to its A position, the center of gravity of the arm itself moves closer to the axis of rotation of the serving head rotor while the center of gravity of the counterweight itself moves away from the axis of rotation of the rotor. However, when the pivotally mounted unit moves from its A position to its C position, the reverse is true regarding the shifting of the center'of gravity of the arm and counterweight, respectively.

Operation The above-described apparatus operates in the following manner:

arrow (Fig. 2) at a relatively high speed, which causes the strands 23-24 to be withdrawn from the cops |3|6 and to be served spirally around the core unit It being advanced by the twisting machine to form the textile covering ll thereover. As the serving operation continues, the diameter of each of the cops |5-|6 gradually decreases so that the free end of the arm 3| moves inwardly from its B position toward the center of the cop l5 and eventually reaches its neutral position (A) (Fig. 2).

When the arm 3| is moving from the B position to the A position, the centrifugal force acting on the arm 3| tends to rotate the arm 3| about its pivot point away from the center of the cop I6 against the action of the spring 35 and thereby decrease the braking effect of the arm on the cop. However, the centrifugal force on the counterweight tends to rotate it about its pivot point in a direction opposite to that-in which the arm tends to rotate, thereby substantially neutralizing the eifect of the centrifugal force acting on the arm 3|. As a result of this neutralization of the centrifugal force actin on the arm 3| as it travels from B to A, the torsion spring 35 is unaffected in its operation and is thereby free to exert the required brakin force on the cop 26 through the arm 3 I.

As the unwinding diameter of the cop decreases, the arm 3| moves from the neutral position (A) to its innermost braking position (C). When the arm 3| is moving from the A position to the C position, the action of centrifugal force tends to rotate the arm 3| toward the center of the cop I6 and thereby to increase the braking effect of the arm on the cop and, consequently, to increase the tension on the strands 24-44 being withdrawn therefrom. However, this action is again substantially neutralized by the effect of the centrifugal force acting on the counterweight so that the braking effect exerted on the cop by the arm 31 through this portion of its travel is still controlled by the torsion spring 35.

It should be noted that, as the arm 3| travels from its B position to its A position, the centrifugal force acting on the arm progressively decreases because the center of gravity of the arm.

itself moves closer to the axis of rotation of the serving head rotor. At the same time, however. the centrifugal force acting on the counterweight progressively increases due to the shifting of its center of gravity away from the axis of rotation of the serving head rotor. The result of the forces actin on the arm and counterweight is such that a slight overbalancing effect occurs which causes the arm 3| to be urged toward the center of the cop and thereby assists the spring 35 in maintaining constant tension on the strand 24 during this portion of travel of the brake arm 3|. By the same token, as the arm 3| moves from its A position to its C position, the result of the centrifugal forces acting on the arm 3| and the counterweight 44 is such that a slight overbalancing effect occurs which urges the arm 3| toward the center of the cop, and thereby assists the spring 35 in maintaining uniform tension on the strand during this portion of travel of the arm. Obviously, then, when the arm is moving from its B position to it C position, the torsion spring 35 never has to work against the effect of the centrifugal force acting on the arm 3| and the counterweight 44 and is thereby permitted to produce the required braking effect on the cop. On the other hand, the resultant effect of the centrifugal force acting on the arm and counterweight is a small force working with the torsion spring so as to assist the spring in maintaining uniform tension on the strand throughout its entire unwinding operation from the cop.

As the arm 3| moves from its B position to its C position, it is obvious that the torsion spring causing such movement is substantially unloaded, that is, the spring is gradually unwinding and, therefore, exerts progressively less braking effect on the cop and likewise on the strand 24 being withdrawn therefrom. However, the braking effect exerted on the cop by the arm must progressively decrease in order to maintain a uniform tension on the strand as the unwinding of the strand proceeds from a full cop to an empty cop, because the leverage of the strand with respect to the axis of rotation of the cop is continuously decreasing. In view of this fact, the torsion spring 35 is designed to unload at a rate substantially equal to the rate at which the braking effect on the cop should be reduced. To compensate for the fact that the spring 35 may not unload at a rate exactly equal to that required to maintain uniform tension on the strand 24, the arm 3| is curved so that its contact point with the periphery of the cop moves toward the pivot point of the arm as the arm travels from the B position to the C position thereby producing a progressive decrease in the actual braking length of the arm 3|. This progressive decrease in the actual braking length of the arm assists the torsion spring to maintain uniform tension on the strand being withdrawn from the cop, during that portion of its travel in which the torsion spring is substantially unloaded.

It is believed to be apparent that the counterweight 44 is arranged to substantially neutralize the effect of centrifugal force acting on the brake arm 3| and thereby permits the torsion spring 35 to maintain complete control over the brake arm 3| as it moves from its B position to its C position, that the brake arm is so curved with respect to its respective cop that the actual braking length thereof is progressively shortened as the arm travels in the aforementioned manner and thereby compensates in part for the relaxation of the spring 35 and that the brake 30 is arranged as a unit on the serving head rotor with respect to its respective cop to be tensioned thereby so that its neutral position falls intermediate its outermost and innermost braking positions, whereby the center of gravity of thearm and the counterweight shift with respect to the axis of rotation of the serving head and produce a small force which assists the torsion spring in maintaining uniform tension on the strand. It is readily seen that all of these factors operate together to progressively decrease the braking effect which the brake 30 exerts against the cop I6 and yet at the same time maintain a uniform tension on the strand 24 being withdrawn from the cop I6 during a serving operation on the core l8.

While the above-described strand tensioning apparatus is particulrly well adapted for use with high speed serving heads, it is readily seen that it may be employed to rovide constant tension on strands employed in other high speed apparatus, such as braiders, and the like, without departing from the scope of the invention as defined in the appended claims.

What is claimed is:

1. In a high speed serving head having a plurality of strand supply cops disposed about the central axis thereof, a brake for maintaining uniform tension on a strand being withdrawn from the strand supply cop, which comprises a curved brake arm pivotally mounted on the serving head adjacent to the strand supply to be tensioned thereby, resilient means for continuously urging the free end of said brake arm against the periphery of the cop, said arm being arranged on the serving head with respect to the cop so that it has a neutral position intermediate its outermost braking position and its innermost braking position, at which the action of centrifugal force thereon caused by the rotation of the serving head does not; tend to turn the arm about its pivot point, and means secured on the brake arm for neutralizing the effect of centrifugal force on the brake arm during its travel from its outermost to its innermost braking position, said neutralizing means being so arranged and proportioned on the brake arm that the action of centrifugal force on the brake arm progressively decreases as the arm moves from its outermost braking position to its neutral braking position while the action of centrifugal force on the neutralizing means moving with said arm progressively increases, and vice versa when the arm moves from its neutral braking position to its innermost braking position, whereby the resultant centrifugal force acting on the brake arm assists the resilient means to maintain a substantially uniform tension on the strand being withdrawn from the cop throughout a complete unwinding operation of the strand from a full cop to an empty cop.

2. The combination with a high speed serving head having a plurality of strand supply cops disposed about the central axis thereof, and a brake for continuously engaging the unwinding periphery of a strand supply cop mounted on the serving head, which brake comprises a pivotally mounted arm, a spring for urging the free end of the arm against the periphery of the cop to maintain tension on a strand being withdrawn therefrom, the arm being so curved with respect to the strand supply that the effective length of the brake arm constantly decreases as the strand is unwound from the cop and thereby compensates for the relaxation of the spring, said curved brake arm being so arranged and proportioned that as the arm moves from its outermost braking position against a full cop to its innermost braking position a substantially exhausted cop passes through an intermediate position at which the centrifugal force acting on the arm when the serving head is rotated does not tend to turn the brake arm about its pivot point, said arrangement of the brake arm causes the action of centrifugal force to tend to turn the arm outwardly away from the cop as the arm moves from its outermost braking position to its intermediate braking position and to turn the arm inwardly against the cop as the arm moves from its intermediate braking position to its innermost braking position, and a counterweight positioned on the brake arm adjacent to its pivot point and so arranged and proportioned that the action of centrifugal force acting thereon completely neutralizes the centrifugal force acting on the arm as it moves inwardly to its intermediate position and only partially neutralizes the centrifugal force action on the arm as it moves away from its intermediate position, whereby the resultant effect of the centrifugal force acting on the arm during its latter movement serves to assist the spring to maintain a substantially uniform tension on the strand being withdrawn from the cop.

3. In a high speed serving head having a pinrality of strand supply cops disposed about the central axis thereof, a brake for maintaining uniform tension on a, strand being withdrawn from the strand supply cop, which comprises a curved brake arm pivotally mounted on the serving head adjacent to the strand supply to be tensioned thereby, resilient means for continuously urging the free end of said brake arm against the periphery of the cop to tension a strand being withdrawn therefrom, the curve of said brake arm being so formed that the point of contact between the arm and the periphery of the cop shifts toward the pivot point of said arm as the strand is withdrawn from the cop gradually decreasing the efl'ective length of the brake arm, the decreasing of the length of the brake arm compensates for the relaxation of the resilient urging means as the brake arm moves from its outermost position against a full cop to its innermost braking position against a substantially exhausted cop, said brake arm being so positioned on the serving head that when the serving head is rotated the action of centrifugal force on the arm tends to turn it away from the cop as the arm moves from its outermost braking position to an intermediate braking position and toward the cop as the arm moves from said intermediate position to its innermost braking position, and a counterweight provided on the brake arm directly opposite its pivot point for neutral izing the action of centrifugal force tending to turn the brake arm about its pivot point, said curvedbrake arm and counterweight being so arranged and proportioned with respect to each other that the action of centrifugal force tending to turn the brake arm away from the cop progressively decreases as the arm moves from its outermost braking position to an intermediate braking position while the action of centrifugal force on the counterweight progressively increases, and vice versa as the arm moves from the said intermediate position to its innermost braking position, whereby the resultant action of centrifugal force on the brake arm during its travel from its outermost braking position to its innermost braking position assists the resilient means to maintain a uniform tension on the strand being withdrawn from the cop.

4. In a high speed serving head carrying a plurality of strand supply cops disposed about the central axis thereof, a brake for maintaining uniform tension on a strand being withdrawn from the strand supply cop, which comprises a brake arm pivotally mounted on the serving head adjacent to a strand supply cop carried thereby, resilient means for continuously urging the free end of the brake arm against the periphery of the cop to impart a predetermined tension on the strand being unwound therefrom, said brake arm being so arranged with respect to the central axis of the serving head that its center of gravity moves closer to the central axis of the rotor as the arm is moved by the resilient means from its outermost position against a full cop to an intermediate braking position against partially exhausted cops and then moves away from the axis of the rotor as the arm moves from the said intermediate position to its innermost braking position against an exhausted cop, and means secured on the brake arm in such a position that the effect of centrifugal force acting thereon due to the rotation of the serving head neutralizes the effect of centrifugal force on said brake arm as the arm moves from its outermost position to its intermediate position, and only partially neutralizes the effect of centrifugal force on the arm as it moves from said intermediate position to its innermost position because the centrifugal force acting on the arm gradually increases while the action of centrifugal force on the neutralizing means gradually decreases, whereby the difference between the effect of the centrifugal force on the arm and on the neutralizing means durin the latter movement of the arm assists the resilient means to maintain uniform tension on the strand being unwound from the cop throughout a complete unwinding operation of the strand from a full cop to an empty cop.

5. In a high speed serving head having a plurality of strand supply cops disposed about, the central axis thereof, a brake device for each supply cop for maintaining uniform tension on th strand being withdrawn from the cop, which comprises a curved brake arm pivotally mounted on the serving head rotor adjacent to a strand supply-cop, resilient means for continuously urging the free end of the brake arm against the periphery of the cop to tension a strand being withdraw therefrom, said brake arm being so arranged with respect to the central axis of the serving head that its center of gravity moves closer to the central axis of the rotor as the arm is moved by th resilient means from its outermost position against a full cop to an termediate braking position against a partially exhausted cop and then moves away from the axis of the rotor as the arm moves from the said intermediate position to its innermost braking position against an exhausted cop, said arrangement of the arm causes the centrifugal force acting on the arm when the serving head is rotated to tend'to swing the arm away from the cop against the action of the resilient means while the center of gravity moves closer to the axis of the rotor and to tend to swing the arm toward thecop when its center of gravity moves away from the axis of the rotor, and a counterweight secured on the brake arm adjacent the pivoted end thereof in such a position that its center of gravity moves away from the axis of the serving head as the arm moves toward the said intermediate position and then moves closer to the said axis when the arm moves away from the said intermediate position, said arrangement of the counterweight causes the centrifugal force acting thereon to neutraliz the effect of centrifugal force acting on the arm as it moves from its outermost braking position to its intermediate position and to partially neutralize the effect of centrifugal force on the arm as it moves from its intermediate position to its innermost position,

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,537,638 Jenny May 12, 1925 Van Hook Aug. 26, 1941 

